1. Field of the Invention
This invention relates to continuous casting machines in which liquid metal is charged to a water cooled mold and therein is cooled sufficiently to form a generally vertical strand having a closed shell solidified metal surrounding a still liquid core. The strand thus formed emerges from the lower and open end of the mold to pass downwardly through a strand support system and secondary cooling zone. The strand support system in the secondary cooling zone comprises a plurality of rollers arranged to carry and guide the strand through a curved path to a horizontal run-out table. In particular, this invention relates to a construction of strand support rollers for use such as in the secondary cooling zone of such a casting machine, and which incorporate a new and improved arrangement for lubricating bearings that support such rollers.
2. Description of the Prior Art
A continuous casting machine of a type to which the present invention may be applied, is well known to the prior art and schematically illustrated in such as U.S. Pat. Nos. to Rudolf SChoffmann, 3,589,429, of June 29, 1971 and 3,747,664 of July 24, 1973. As illustrated in both of those patents, liquid metal may be poured into a cooled bottomless mold from which a strand of metal with a still liquid core emerges and is carried through a curved bow section for further cooling, and then to horizontal run-out table. Another patent to Rudolf Schoffmann, U.S. Pat. No. 3,710,847 of Jan. 16, 1973, discloses how rollers may be arranged and supported to carry and guide the cast strand through the curved bow section of such a machine.
The aforementioned patent, U.S. Pat. No. 3,710,847, also discloses (in FIG. 2 thereof) that for supporting a cast strand 1000 to 2000 mm wide with the minimum deflection desired, it is required to mount the strand supporting rollers with support intermediate its ends.
According to the teachings of the prior art, such multi-support roller assemblies have been provided with a fixed shaft, intermediate supports for the nonrotating shaft, bearings on the shaft and cylindrical shell rollers mounted over the bearings to turn freely relative to the nonrotating shaft. The requirement of freely turning rollers under pressure dictates the use of bearings. Sleeve type bearings, or bushings of different materials and antifriction bearings have been used. Regardless of the bearing type, it is imperative that the bearing be protected from contamination, by dirt, scale and water and that lubrication be supplied to the bearings to reduce friction. Some form of mechanical seals such as synthetic lip type, labyrinth or piston rings are used. In conjunction with mechanical seals, which are subject to wear, distortion or destruction from the severe environment of the process, it has been found that grease acts as an excellent bearing seal, lubricant and flushing agent for the slowly turning rollers. Good bearing performance is assured only if the bearing can be kept full of grease during operation and further that the grease be flushed through the bearing at periodic intervals.
Central grease systems are available which consist of reservoirs, pumping units, headers, metering valves and distribution lines which will deliver predetermined quantities of grease to each bearing at periodic intervals. One such system, with several modifications, is disclosed in U.S. Pat. No. 1,805,303, granted May 12, 1931. Another system in which grease is applied to a plurality of locations at a rate responsive to the rate of operation of the machine being greased is disclosed in U.S. Pat. No. 2,885,029 granted May 5, 1959. A more recent patent disclosing a device for delivering a measured quantity of grease to a plurality of locations at predetermined time intervals in U.S. Pat. No. 3,329,319 of 1967. When such systems are applied to the bow rollers for supporting a cast strand in a continuous casting machine, the metering valves which distribute measured quantities of grease from the headers to the bearings are usually mounted on or near the support structure for the equipment. Tubing and fittings connect the supply headers to the metering valve inlets and then additional tubing or flexible hoses connect the metering valve outlets to roll shaft retainer plates. The roll shafts and roll shaft retainer plates have drilled grease passages which conduct the grease to each bearing. The large number of bearings in a continuous casting machine requires the extensive use of metering valves, tubing, flexible hose and fittings. The lubrication system, with all its appurtenances, can obstruct access to the machine, complicate maintenance, delay replacement of equipment and increase facility downtime.